Lotfi Grine, Eng. – Product Specialist at Robco Causes for bolts to loosen in service: · Vibration: it’s an unintentional loosening, and it is the repeated relative displacements between the contact surfaces resulting in relative motion occurring in the threads. · Gasket creep: the gasket loses its springiness over time; it is also a permanent deformation and It’s more severe in high-temperature applications. · Elastic interactions between multiple bolts: Elastic interactions can either increase or decrease bolt preload. · Temperature fluctuation caused as a result of either differences in temperature or differences in clamped materials. · Low preload developed at installation: it occurs when there is no sufficient clamp force (under-tightened bolt) present on the joint interface to prevent relative motion...
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